Recognition: unknown
Solvable Descent and the Grunwald Problem for Solvable Groups
Pith reviewed 2026-05-10 03:52 UTC · model grok-4.3
The pith
Solvable descent via a fibration theorem gives a positive answer to the Grunwald problem for solvable groups up to the Brauer-Manin obstruction.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The central discovery is a fibration theorem over quasi-trivial tori that implies solvable descent. This in turn solves the Grunwald problem for solvable groups up to the necessary Brauer-Manin obstruction. The key step involves computing the triple variation of the obstruction on grids of fibers, which reduces to a linear combination of Redei symbols on the base, and then applying a combinatorial principle to ensure the obstruction vanishes in at least one fiber.
What carries the argument
The fibration theorem over quasi-trivial tori together with the computation of the triple variation of the Brauer-Manin obstruction as a linear combination of Redei symbols.
If this is right
- The Grunwald problem has a positive answer for solvable groups up to the Brauer-Manin obstruction.
- This provides a generalization of Shafarevich's theorem on the inverse Galois problem for solvable groups.
- An alternative proof of Shafarevich's result is given that avoids the shrinking procedure.
Where Pith is reading between the lines
- The method may extend to other Galois realization problems if analogous fibrations can be found.
- The combinatorial principle from Smith could apply to related vanishing problems in arithmetic geometry.
- Explicit examples of the required Galois extensions might be constructed using the fiber grids described.
Load-bearing premise
The suitable fibration theorem over quasi-trivial tori holds and the triple variation of the Brauer-Manin obstruction reduces to a linear combination of Redei symbols whose vanishing can be inferred combinatorially in at least one fiber.
What would settle it
A concrete solvable group and collection of local conditions where the Brauer-Manin obstruction vanishes but no global extension realizing the group with those local behaviors exists.
read the original abstract
We prove a suitable fibration theorem over quasi-trivial tori that, through an approach developed by Harpaz and Wittenberg, implies so-called solvable descent. In particular, this gives a positive answer to the Grunwald problem for solvable groups up to the necessary Brauer--Manin obstruction, providing a generalizion of Shafarevich's positive answer to the Inverse Galois Problem for solvable groups. This also provides an alternative proof of Shafarevich's result that avoids his "shrinking procedure". For the fibration theorem, we first adapt the starting ideas of Shafarevich for the creation of local lifts. To deal then with the Brauer--Manin obstruction (i.e. the relevant local-to-global obstruction), we compute its "triple variation" on grids of fibers. The resulting expression is a linear combination of Red\'ei symbols on the base. Customizing these and employing a combinatorial principle first noted by Alexander Smith in the context of Class and Selmer Groups, one infers the vanishing of the obstruction in at least one fiber.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper proves a fibration theorem over quasi-trivial tori by adapting Shafarevich's constructions of local lifts. Combined with the Harpaz-Wittenberg framework, this yields solvable descent. As a consequence, the Grunwald problem for solvable groups admits a positive answer up to the Brauer-Manin obstruction; the same argument supplies an alternative proof of Shafarevich's theorem on the inverse Galois problem for solvable groups that avoids the shrinking procedure. The central technical step is the computation of the triple variation of the Brauer-Manin obstruction on grids of fibers, which is shown to equal a linear combination of Redei symbols on the base; a combinatorial vanishing principle of Smith is then applied to guarantee that the obstruction vanishes for at least one fiber.
Significance. If the fibration theorem is established and the coefficients in the Redei-symbol combination are shown to satisfy the hypotheses of Smith's principle in this arithmetic-geometric setting, the result would give a substantial generalization of Shafarevich's theorem to the Grunwald problem and a new route to solvable descent that integrates modern obstruction theory with classical local-lift techniques.
major comments (2)
- [section on triple variation of the Brauer-Manin obstruction] The manuscript must supply an explicit verification that the precise linear combination of Redei symbols obtained from the triple variation on the grids of fibers satisfies the independence and support conditions required by Smith's combinatorial principle (as stated in the context of class groups and Selmer groups). Without this check, the inference that the combination vanishes on at least one fiber does not follow. This identification is load-bearing for the solvable-descent conclusion.
- [fibration theorem section] The adaptation of Shafarevich's local-lift ideas to produce the fibration over a quasi-trivial torus requires a detailed statement and proof of the fibration theorem itself (including the precise base and fiber properties). The abstract outlines the strategy but the load-bearing existence claim for the fibration must be fully substantiated before the subsequent obstruction computation can be applied.
minor comments (2)
- Notation for the triple variation and the grids of fibers should be introduced with a clear diagram or explicit indexing to aid readability.
- The precise reference to the version of Smith's combinatorial principle being invoked (including any modifications needed for the Redei-symbol setting) should be stated explicitly.
Simulated Author's Rebuttal
We thank the referee for the careful reading of our manuscript and for the constructive comments, which help clarify the presentation of the key technical steps. We address each major comment in turn below.
read point-by-point responses
-
Referee: [section on triple variation of the Brauer-Manin obstruction] The manuscript must supply an explicit verification that the precise linear combination of Redei symbols obtained from the triple variation on the grids of fibers satisfies the independence and support conditions required by Smith's combinatorial principle (as stated in the context of class groups and Selmer groups). Without this check, the inference that the combination vanishes on at least one fiber does not follow. This identification is load-bearing for the solvable-descent conclusion.
Authors: We agree that an explicit verification is required to make the application of Smith's combinatorial principle fully rigorous in this setting. While the manuscript describes the customization of the Redei symbols arising from the triple variation and invokes the principle to conclude vanishing on at least one fiber, we acknowledge that the independence and support conditions are not checked in sufficient detail. In the revised manuscript we will insert a dedicated paragraph (or short subsection) that verifies these conditions directly for the linear combination obtained from the grids of fibers, confirming that the hypotheses of the principle hold in the arithmetic-geometric context at hand. revision: yes
-
Referee: [fibration theorem section] The adaptation of Shafarevich's local-lift ideas to produce the fibration over a quasi-trivial torus requires a detailed statement and proof of the fibration theorem itself (including the precise base and fiber properties). The abstract outlines the strategy but the load-bearing existence claim for the fibration must be fully substantiated before the subsequent obstruction computation can be applied.
Authors: The fibration theorem is stated and proved in the body of the paper by adapting Shafarevich's local-lift constructions to the case of quasi-trivial tori. Nevertheless, we accept that the current exposition would benefit from a more self-contained formulation. In the revision we will expand the statement of the theorem to include explicit descriptions of the base (a quasi-trivial torus) and the geometric properties of the fibers, and we will add a few additional paragraphs in the proof that spell out the local-lift steps in greater detail, thereby making the existence claim fully substantiated before the Brauer-Manin computation begins. revision: yes
Circularity Check
No circularity: derivation uses external techniques and principles without self-referential reduction
full rationale
The paper proves a fibration theorem by adapting Shafarevich's local lift ideas and applies the Harpaz-Wittenberg approach to obtain solvable descent. The Brauer-Manin obstruction is handled by computing a triple variation that reduces to a linear combination of Redei symbols, then invoking Smith's external combinatorial principle to guarantee vanishing on some fiber. No equations or steps in the described chain define a quantity in terms of itself, rename a fitted input as a prediction, or rely on load-bearing self-citations whose content reduces to the present work. The central claims remain independent of the paper's own inputs and rest on externally verifiable results.
Axiom & Free-Parameter Ledger
axioms (2)
- domain assumption A suitable fibration theorem over quasi-trivial tori exists and can be adapted from Shafarevich's local lift ideas.
- domain assumption The triple variation of the Brauer-Manin obstruction on grids of fibers is a linear combination of Redei symbols.
Forward citations
Cited by 1 Pith paper
-
Real approximation for homogeneous spaces with finite stabilizers
Finite k-groups split by 2-primary extensions satisfy real approximation on homogeneous spaces with finite stabilizers.
Reference graph
Works this paper leans on
-
[1]
Cao, Yang and Demarche, Cyril and Xu, Fei , TITLE =. Trans. Amer. Math. Soc. , FJOURNAL =. 2019 , NUMBER =
2019
-
[2]
Cao, Yang and Liang, Yongqi , TITLE =. Adv. Math. , FJOURNAL =. 2022 , PAGES =. doi:10.1016/j.aim.2022.108718 , URL =
-
[3]
Bright, M. J. and Browning, T. D. and Loughran, D. , TITLE =. Compos. Math. , FJOURNAL =. 2016 , NUMBER =. doi:10.1112/S0010437X16007405 , URL =
-
[4]
Hasse principle and weak approximation for pencils of
Colliot-Th\'. Hasse principle and weak approximation for pencils of. J. Reine Angew. Math. , FJOURNAL =. 1994 , PAGES =. doi:10.1515/crll.1994.453.49 , URL =
-
[5]
Deninger, Ch. , TITLE =. J. Pure Appl. Algebra , FJOURNAL =. 1988 , NUMBER =. doi:10.1016/0022-4049(88)90102-8 , URL =
-
[6]
Gille, Philippe and Pianzola, Arturo , TITLE =. J. Pure Appl. Algebra , FJOURNAL =. 2008 , NUMBER =. doi:10.1016/j.jpaa.2007.07.005 , URL =
-
[7]
Tate, J. T. , TITLE =. Algebraic. 1967 , MRCLASS =
1967
-
[8]
Lang, Serge , TITLE =. 1994 , PAGES =. doi:10.1007/978-1-4612-0853-2 , URL =
-
[9]
Lang, Serge , TITLE =. 1983 , PAGES =. doi:10.1007/978-1-4757-1810-2 , URL =
-
[10]
Verdier, Jean-Louis , TITLE =. Ast\'. 1996 , PAGES =
1996
-
[11]
Algebraic number theory , url =
Neukirch, J\"urgen , TITLE =. 1999 , PAGES =. doi:10.1007/978-3-662-03983-0 , URL =
-
[12]
Zhu, Yi , TITLE =. J. Inst. Math. Jussieu , FJOURNAL =. 2019 , NUMBER =. doi:10.1017/s1474748017000081 , URL =
-
[13]
1970 , PAGES =
Raynaud, Michel , TITLE =. 1970 , PAGES =
1970
-
[14]
The 8-rank of the narrow class group and the negative Pell equation , volume=
Chan, Stephanie and Koymans, Peter and Milovic, Djordjo and Pagano, Carlo , year=. The 8-rank of the narrow class group and the negative Pell equation , volume=. doi:10.1017/fms.2022.40 , journal=
-
[15]
The distribution of ^ -Selmer groups in degree twist families I. arXiv e-prints , keywords =. doi:10.48550/arXiv.2207.05674 , archivePrefix =. 2207.05674 , primaryClass =
-
[16]
and Grothendieck, A
Giraud, J. and Grothendieck, A. and Kleiman, S. L. and Raynaud, M. and Tate, J. , TITLE =. 1968 , PAGES =
1968
-
[17]
Grothendieck, Alexander , TITLE =. Tohoku Math. J. (2) , FJOURNAL =. 1957 , PAGES =. doi:10.2748/tmj/1178244839 , URL =
-
[19]
Sums of rational cubes and the 3 -Selmer group. arXiv e-prints , keywords =. doi:10.48550/arXiv.2405.09311 , archivePrefix =. 2405.09311 , primaryClass =
-
[20]
Walker, J. R. , TITLE =. Fund. Math. , FJOURNAL =. 1974 , PAGES =. doi:10.4064/fm-85-3-229-233 , URL =
-
[21]
Bauer, Heinz , TITLE =. Arch. Math. , FJOURNAL =. 1959 , PAGES =. doi:10.1007/BF01240814 , URL =
-
[22]
2007 , PAGES =
Voisin, Claire , TITLE =. 2007 , PAGES =
2007
-
[23]
Gelfand, Sergei I. and Manin, Yuri I. , TITLE =. 2003 , PAGES =. doi:10.1007/978-3-662-12492-5 , URL =
-
[24]
and Griffith, Phillip A
Fossum, Robert M. and Griffith, Phillip A. and Reiten, Idun , TITLE =. 1975 , PAGES =
1975
-
[25]
Leary, Ian J. , TITLE =. J. Algebra , FJOURNAL =. 1997 , NUMBER =. doi:10.1006/jabr.1997.7151 , URL =
-
[26]
Nakaoka, Minoru , TITLE =. Ann. of Math. (2) , FJOURNAL =. 1961 , PAGES =. doi:10.2307/1970333 , URL =
-
[27]
Reichstein, Zinovy and Youssin, Boris , TITLE =. Canad. J. Math. , FJOURNAL =. 2000 , NUMBER =. doi:10.4153/CJM-2000-043-5 , URL =
-
[28]
Tamme, G\". Introduction to \'. 1994 , PAGES =. doi:10.1007/978-3-642-78421-7 , URL =
-
[29]
Schneider, Peter , TITLE =. Math. Z. , FJOURNAL =. 1979 , NUMBER =. doi:10.1007/BF01214195 , URL =
-
[30]
On solvable number fields , JOURNAL =
Neukirch, J\". On solvable number fields , JOURNAL =. 1979 , NUMBER =. doi:10.1007/BF01390030 , URL =
-
[31]
1954 , PAGES =
On an existence theorem in the theory of algebraic numbers , JOURNAL =. 1954 , PAGES =
1954
-
[32]
Higher dimensional varieties and rational points (
Koll\'. Rationally connected varieties and fundamental groups , BOOKTITLE =. 2003 , MRCLASS =. doi:10.1007/978-3-662-05123-8\_4 , URL =
-
[33]
, TITLE =
Grothendieck, A. , TITLE =. Inst. Hautes \'. 1966 , PAGES =
1966
-
[34]
Poonen, Bjorn , TITLE =. 2017 , PAGES =. doi:10.1090/gsm/186 , URL =
-
[35]
The Brauer Group of a Commutative Ring , volume =
Maurice Auslander and Oscar Goldman , journal =. The Brauer Group of a Commutative Ring , volume =
-
[36]
1982 , publisher=
Gesammelte Abhandlungen , author=. 1982 , publisher=
1982
-
[37]
Cyril Demarche and Giancarlo Lucchini Arteche and Danny Neftin , title =. doi:10.5802/aif.3104 , url =
-
[38]
Milne , title=
J.S. Milne , title=. 2006 , publisher=
2006
-
[39]
Hironaka, Heisuke , TITLE =. Ann. of Math. (2). 1964 , PAGES =. doi:10.2307/1970547 , URL =
-
[40]
Demeio , TITLE=
Julian L. Demeio , TITLE=
-
[41]
The Brauer group of tori. arXiv e-prints , keywords =. doi:10.48550/arXiv.2410.20616 , archivePrefix =. 2410.20616 , primaryClass =
-
[42]
Harpaz, Yonatan and Skorobogatov, Alexei N. , TITLE =. Algebra Number Theory , FJOURNAL =. 2016 , NUMBER =. doi:10.2140/ant.2016.10.813 , URL =
-
[43]
Kim, Dohyeong and Morishita, Masanori , TITLE =. Res. Number Theory , FJOURNAL =. 2025 , NUMBER =. doi:10.1007/s40993-025-00648-4 , URL =
-
[44]
Friedlander, J. B. and Iwaniec, H. and Mazur, B. and Rubin, K. , TITLE =. Invent. Math. , FJOURNAL =. 2013 , NUMBER =. doi:10.1007/s00222-012-0438-8 , URL =
-
[45]
Stevenhagen, Peter , TITLE =. Math. Proc. Cambridge Philos. Soc. , FJOURNAL =. 2022 , NUMBER =. doi:10.1017/s0305004121000335 , URL =
-
[46]
Park City lecture notes: around the inverse Galois problem. arXiv e-prints , keywords =. doi:10.48550/arXiv.2302.13719 , archivePrefix =. 2302.13719 , primaryClass =
-
[47]
P\'. Brauer-. Int. J. Number Theory , FJOURNAL =. 2022 , NUMBER =. doi:10.1142/S1793042122500786 , URL =
-
[48]
Wang, Shianghaw , TITLE =. Ann. of Math. (2) , FJOURNAL =. 1950 , PAGES =. doi:10.2307/1969335 , URL =
-
[49]
Algebra Number Theory , FJOURNAL =
Harpaz, Yonatan and Wittenberg, Olivier , TITLE =. Algebra Number Theory , FJOURNAL =. 2024 , NUMBER =. doi:10.2140/ant.2024.18.787 , URL =
-
[51]
Swinnerton-Dyer, Peter , TITLE =. Ann. Sci. \'. 2001 , NUMBER =. doi:10.1016/S0012-9593(01)01080-1 , URL =
-
[52]
Chernousov, Vladimir , TITLE =. Dokl. Akad. Nauk SSSR , FJOURNAL =. 1989 , NUMBER =
1989
-
[53]
Popov, Vladimir L. , title =. Mathematics of the. doi:10.1070/im1974v008n02abeh002107 , url =
-
[54]
Lucchini Arteche, Giancarlo , TITLE =. Trans. Amer. Math. Soc. , FJOURNAL =. 2019 , NUMBER =. doi:10.1090/tran/7796 , URL =
-
[55]
Demarche, Cyril and Lucchini Arteche, Giancarlo and Neftin, Danny , TITLE =. Ann. Inst. Fourier (Grenoble) , FJOURNAL =. 2017 , NUMBER =
2017
-
[56]
Bosch, Siegfried and L\". N\'. 1990 , PAGES =. doi:10.1007/978-3-642-51438-8 , URL =
-
[57]
Poonen, Bjorn and Stoll, Michael , TITLE =. Ann. of Math. (2) , FJOURNAL =. 1999 , NUMBER =. doi:10.2307/121064 , URL =
-
[58]
2009 , school=
Méthodes cohomologiques pour l’étude des points rationnels sur les espaces homogènes. 2009 , school=
2009
-
[59]
Friedrich Knop and Hanspeter Kraft and Thierry Vust , title =. Algebraische. doi:10.1007/978-3-0348-7662-9_5 , url =
-
[60]
doi:10.1515/crll.2005.2005.582.143 , journal =
Harari, David and Szamuely, Tam\'. Arithmetic duality theorems for 1-motives , JOURNAL =. 2005 , PAGES =. doi:10.1515/crll.2005.2005.578.93 , URL =
-
[61]
and Colliot-Thélène, Jean-Louis and Skorobogatov, Alexei N
Borovoi, Mikhail V. and Colliot-Thélène, Jean-Louis and Skorobogatov, Alexei N. The elementary obstruction and homogeneous spaces. Duke Math. J. 2008. doi:10.1215/S0012-7094-08-14124-9
-
[62]
Borovoi, Mikhail V. , TITLE =. Internat. Math. Res. Notices , volume =. 1996 , NUMBER =. doi:10.1155/S1073792896000268 , URL =
-
[63]
Preprint , volume=
Some remarks on strong approximation and applications to homogeneous spaces of linear algebraic groups. Preprint , volume=
-
[64]
\"Uber die
Hilbert, David , journal =. \"Uber die
-
[65]
Demarche, Cyril , TITLE =. Bull. Soc. Math. France , FJOURNAL =. 2017 , NUMBER =. doi:10.24033/bsmf.2735 , URL =
-
[66]
Corvaja, Pietro and Zannier, Umberto , TITLE =. Math. Z. , FJOURNAL =. 2017 , NUMBER =. doi:10.1007/s00209-016-1775-x , URL =
-
[67]
Principal homogeneous spaces under flasque tori: applications , JOURNAL =
Colliot-Th\'. Principal homogeneous spaces under flasque tori: applications , JOURNAL =. 1987 , NUMBER =. doi:10.1016/0021-8693(87)90026-3 , URL =
-
[68]
Sansuc, J.-J. , TITLE =. J. Reine Angew. Math. , FJOURNAL =. 1981 , PAGES =. doi:10.1515/crll.1981.327.12 , URL =
-
[69]
La descente sur les vari\'
Colliot-Th\'. La descente sur les vari\'. Journ\'. 1980 , MRCLASS =
1980
-
[70]
1973 , PAGES =
Serre, Jean-Pierre , TITLE =. 1973 , PAGES =
1973
-
[71]
Ekedahl, Torsten , TITLE =. S\'. 1990 , MRCLASS =
1990
-
[72]
Saltman, David J. , TITLE =. Invent. Math. , FJOURNAL =. 1984 , NUMBER =. doi:10.1007/BF01389135 , URL =
-
[73]
Swan, Richard G. , TITLE =. Invent. Math. , FJOURNAL =. 1969 , PAGES =. doi:10.1007/BF01389798 , URL =
-
[74]
Noether, Emmy , TITLE =. Math. Ann. , FJOURNAL =. 1917 , NUMBER =. doi:10.1007/BF01457099 , URL =
-
[75]
Poonen, Bjorn , TITLE =. Ann. of Math. (2) , FJOURNAL =. 2010 , NUMBER =. doi:10.4007/annals.2010.171.2157 , URL =
-
[76]
arXiv e-prints , keywords =
Brauer and \'E tale H omotopy O bstructions to R ational P oints on O pen C overs. arXiv e-prints , keywords =
-
[77]
Borovoi, Mikhail V. , TITLE =. J. Reine Angew. Math. , FJOURNAL =. 1996 , PAGES =. doi:10.1515/crll.1995.473.181 , URL =
-
[78]
Salberger, Per and Skorobogatov, Alexei N. , TITLE =. Duke Math. J. , FJOURNAL =. 1991 , NUMBER =. doi:10.1215/S0012-7094-91-06322-2 , URL =
-
[79]
Surfaces rationnelles fibr\'
Colliot-Th\'. Surfaces rationnelles fibr\'. S\'. 1990 , MRCLASS =
1990
-
[80]
Skorobogatov, A. N. , TITLE =. S\'. 1990 , ISBN =
1990
-
[81]
Harari, David , title =. Bulletin de la Soci. doi:10.24033/bsmf.2545 , url =
-
[82]
doi:10.1007/978-3-030-43901-9 , url =
Harari, David , title =. doi:10.1007/978-3-030-43901-9 , url =
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.